Methods of forming a reaction product and methods of forming a conductive metal silicide by reaction of metal with silicon

ABSTRACT

A method of forming a reaction product includes providing a semiconductor substrate comprising a first material. A second material is formed over the first material. The first and second materials are of different compositions, and are proximate one another at an interface. The first and second materials as being proximate one another at the interface are capable of reacting with one another at some minimum reaction temperature when in an inert non-plasma atmosphere at a pressure. The interface is provided at a processing temperature which is at least 50° C. below the minimum reaction temperature, and is provided at the pressure. With the interface at the processing temperature and at the pressure, the substrate is exposed to a plasma effective to impart a reaction of the first material with the second material to form a reaction product third material of the first and second materials over the first material. Other aspects and implementations are contemplated.

TECHNICAL FIELD

This invention relates to methods of forming a reaction product and tomethods of forming a conductive metal silicide by reaction of metal withsilicon.

BACKGROUND OF THE INVENTION

Integrated circuits typically use various combinations of insulativematerials, conductive materials, and semiconductive materials (includingconductively doped semiconductive materials). One type of conductivematerial which is utilized is elemental metals. In the context of thisdocument, an “elemental metal” is defined to mean any one or more metalelement(s) in element form, including any alloy of two or more metalelements. In many instances, it is desired to form a metal intoelectrical connection with a crystalline silicon substrate, for exampleconductively doped crystalline silicon. However, the physical contact ofan elemental metal with a crystalline silicon substrate inherentlycreates undesired excessive electrical resistance between the twomaterials.

One common way of reducing this resistance is to form an interfacingsilicide region at the junction or interface of the metal with thesilicon. Thereby, a silicon-silicide-metal interfacing electricalconnection is formed. One manner of forming the silicide is merely byheating the substrate with the two contacting layers to a suitably hightemperature for a sufficient period of time, typically in an inertatmosphere, to cause a reaction of metal and silicon to form the metalsilicide. However in some instances, it might be problematic or at leastundesirable to expose the substrate to the minimum temperature at whichthe silicide will form.

Further, integrated circuitry fabrication continues to strive to makeever denser and smaller electronic devices of the circuitry. One placewhere silicide contact structures are utilized is in the electricalconnection of source/drain diffusion regions of field effect transistorswith overlying conductive metal lines. As the device components getsmaller and denser, it is highly desirable to precisely control theamount of silicide which is formed in such contacts, as well as in otherdevices where silicide interfaces between metal and silicon are desiredto be formed. This is at least in part due to thermal energy required todrive the silicidation reaction, which can lead to thickness variationof the silicide formed over different areas of the substrate and toundesired suicide roughness which can cause shorts in the finishedcircuitry.

For example in some instances in present-generation processing, it isdesirable to fabricate the silicide regions over the substrates to havethicknesses of from 50 Angstroms to 100 Angstroms. Further, it isexpected that the thickness of silicide regions in later-generationprocessing will fall below 50 Angstroms. Regardless, the variation inthickness of silicide regions formed over a substrate using typicalprior art processing has been found to be anywhere from 20 Angstroms to25 Angstroms across the substrate. This variability is undesirable andconstitutes a 20% to 25% thickness variation for desired 100 Angstromsthick silicide regions, and a 40% to 50% variation in thickness fordesired 50 Angstroms thick silicide regions. It would be desirable todevelop methods which enable tighter thickness control of silicideregions which are formed across a substrate, and particularly where thesilicide regions being formed have thicknesses that are no greater than100 Angstroms where the above problem particularly manifests.

While the invention was motivated in addressing the above issues, it isin no way so limited. The invention is only limited by the accompanyingclaims as literally worded, without interpretative or other limitingreference to the specification, and in accordance with the doctrine ofequivalents.

SUMMARY

The invention comprises methods of forming a reaction product andmethods of forming a conductive metal suicide by reaction of metal withsilicon. In one implementation, a method of forming a reaction productincludes providing a semiconductor substrate comprising a firstmaterial. A second material is formed over the first material. The firstand second materials are of different compositions, and are proximateone another at an interface. The first and second materials as beingproximate one another at the interface are capable of reacting with oneanother at some minimum reaction temperature when in an inert non-plasmaatmosphere at a pressure. The interface is provided at a processingtemperature which is at least 50° C. below the minimum reactiontemperature, and is provided at the pressure. With the interface at theprocessing temperature and at the pressure, the substrate is exposed toa plasma effective to impart a reaction of the first material with thesecond material to form a reaction product third material of the firstand second materials over the first material.

In one implementation, a method of forming a conductive metal silicideby reaction of metal with silicon includes providing a semiconductorsubstrate comprising a first material, where the first materialcomprises silicon in elemental form. A second material is formed overthe first material. The second material comprises at least one of anelemental metal or a metal compound rich in metal. The first and secondmaterials are received proximate one another at an interface. The firstand second materials as being proximate one another at the interface arecapable of reacting with one another at some minimum reactiontemperature when in an inert non-plasma atmosphere at a pressure to forma metal silicide. The interface is provided at a processing temperaturewhich is at least 50° C. below the minimum reaction temperature and atthe pressure. With the interface at the processing temperature and atthe pressure, the substrate is exposed to a plasma effective to impart areaction of the first material with the second material to form a metalsilicide on the first material. The plasma is inert to reaction withboth the silicon and the at least one of the elemental metal and themetal compound, and inert to deposition of material over the secondmaterial.

Other aspects and implementations are contemplated.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

FIG. 1 is a diagrammatic sectional view of a semiconductor waferfragment in process in accordance with an aspect of the invention.

FIG. 2 is a view of the FIG. 1 fragment at a processing step subsequentto that shown by FIG. 1.

FIG. 3 is a diagrammatic sectional view of an alternate embodimentsemiconductor wafer fragment in process in accordance with an aspect ofthe invention.

FIG. 4 is a view of the FIG. 3 fragment at a processing step subsequentto that shown by FIG. 4.

FIG. 5 is a diagrammatic equation of exemplary process aspects inaccordance with a part of the invention.

FIG. 6 is a diagrammatic equation of exemplary process aspects inaccordance with a part of the invention.

FIG. 7 is a diagrammatic equation of exemplary process aspects inaccordance with a part of the invention.

FIG. 8 is a diagrammatic equation of exemplary process aspects inaccordance with a part of the invention.

FIG. 9 is a diagrammatic equation of exemplary process aspects inaccordance with a part of the invention.

FIG. 10 is a diagrammatic equation of exemplary process aspects inaccordance with a part of the invention.

FIG. 11 is a diagrammatic equation of exemplary process aspects inaccordance with a part of the invention.

FIG. 12 is a diagrammatic equation of exemplary process aspects inaccordance with a part of the invention.

FIG. 13 is a diagrammatic equation of exemplary process aspects inaccordance with a part of the invention.

FIG. 14 is a diagrammatic equation of exemplary process aspects inaccordance with a part of the invention.

FIG. 15 is a diagrammatic equation of exemplary process aspects inaccordance with a part of the invention.

FIG. 16 is a diagrammatic equation of exemplary process aspects inaccordance with a part of the invention.

FIG. 17 is a diagrammatic equation of exemplary process aspects inaccordance with a part of the invention.

FIG. 18 is a diagrammatic equation of exemplary process aspects inaccordance with a part of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of theconstitutional purposes of the U.S. Patent Laws “to promote the progressof science and useful arts” (Article 1, Section 8).

Exemplary preferred methods of forming reaction products, includingconductive metal silicides by the reaction of metal with silicon, aredescribed with reference to FIGS. 1–18. FIG. 1 diagrammatically depictsa semiconductor substrate indicated generally with reference numeral 10.In the context of this document, the term “semiconductor substrate” or“semiconductive substrate” is defined to mean any constructioncomprising semiconductive material, including, but not limited to, bulksemiconductive materials such as a semiconductive wafer (either alone orin assemblies comprising other materials thereon), and semiconductivematerial layers (either alone or in assemblies comprising othermaterials). The term “substrate” refers to any supporting structure,including, but not limited to, the semiconductive substrates describedabove.

Semiconductor substrate 10 comprises some first material A having somesecond material B formed thereover. First material A and second materialB are of different compositions and are received proximate one anotherat an interface 12. In the illustrated exemplary preferred embodiment ofFIG. 1, first material A and second material B contact one another atinterface 12. FIG. 3 illustrates an alternate exemplary embodimentsemiconductor substrate 10 a. Like numerals from the first describedembodiment are utilized where appropriate, with differences beingindicated with the suffix “a” or with different numerals. Interface 12 aof semiconductor substrate 10 a in FIG. 3 is characterized by a layer orlayers 14 interposed between first material A and second material B suchthat these materials are not contacting one another at interface 12 a.Regardless, first material A and second material B as being proximateone another at interface 12/12 a are capable of reacting with oneanother at some minimum reaction temperature when in an inert non-plasmaatmosphere at some selected pressure. Accordingly, even where firstmaterial A and second material B are not contacting one another,conditions can exist where, at some minimum reaction temperature, one orboth of materials A and B effectively diffuse through layer(s) 14effective to impart a reaction of one with the other. In the context ofthis document, a material A being proximate a material B requires eithera contacting relationship or separation of materials A and B from oneanother by one or more materials in an area of reaction wherein theseparation distance is no greater than 50 Angstroms.

Interface 12/12 a is provided at a processing temperature which is atleast 50° C. below the stated minimum reaction temperature. Further, theinterface is also provided at the pressure referred to above at whichthe above-stated reacting can occur if at or above the minimum reactiontemperature at such pressure. Accordingly, the interface provided asjust so stated does not result in the reaction of material A withmaterial B at this point in the process. Preferably, the processingtemperature at which the interface is provided is no greater than 300°C. below such minimum reaction temperature, more preferably no greaterthan 100° C. below the minimum reaction temperature, even morepreferably no greater than 75° C. below the minimum reactiontemperature, and further preferably no greater than 60° C. below theminimum reaction temperature. For example, titanium metal received onsilicon has a minimum reaction temperature in the absence of plasma of600° C. at 10 Torr. In one exemplary aspect with these materials, theprocessing temperature is provided to be not greater than 550° C., inone embodiment from 300° C. to 550° C., in one embodiment from 500° C.to 550° C., in one embodiment from 525° C. to 550° C., and in oneembodiment from 540° C. to 550° C., and at 10 Torr with no appreciablereaction occurring to form titanium silicide. The artisan knows or canreadily determine the minimum reaction temperature at a given pressurein a non-plasma inert atmosphere for reaction capable first and secondmaterials that are received proximate one another.

Referring to FIGS. 2 and 4, and with interface 12/12 a at the processingtemperature and pressure, substrate 10/10 a is exposed to a plasmaeffective to impart a reaction of first material A with second materialB to form a reaction product third material AB of first material A andsecond material B over first material A. Plasma exposure can start priorto the interface being at the minimum reaction temperature and at thepressure or start after the interface is already at the minimum reactiontemperature and at the pressure. Regardless in such processing, all ofmaterial B might react to form AB, or only a portion thereof might soreact thus forming a B-AB-A composite. Accordingly and regardless, areaction of A and B to form AB is imparted at a temperature below whichsuch would otherwise occur at the pressure the substrate is at.Therefore, second material B should not be too thick to preclude thestated reaction from occurring at interface 12/12 a. In one exemplarypreferred embodiment, it is expected that second material B shouldthereby be formed to a thickness no greater than 75 Angstroms, and morepreferably to a thickness no greater than 25 Angstroms. However, such isexpected to be dependent upon the plasma ion energy and plasma densityutilized, and the density and other attributes of second material B.Regardless in one exemplary preferred embodiment, the plasma during theexposing has a density from 1×10¹¹ ions/cm³ to 1×10¹³ ions/cm³. Further,the plasma exposing preferably comprises some substrate bias tofacilitate the targeting of the plasma at the substrate. Preferably, thesubstrate bias is at a frequency of about 400 kHz or 13.56 mHz. Where abias voltage is utilized, such is preferably no greater than 100V. Anexemplary preferred pressure range for the processing is from 1 mTorr to20 Torr, and with plasma power at from 100 Watts to 5000 Watts. Anothermethod uses inductively coupled plasma to create the plasma (separatefrom substrate bias) to get independent control of plasma ion energy andplasma ion density.

In one preferred implementation, the plasma to which the substrate isexposed is inert to reaction with both first material A and secondmaterial B, and inert to the deposition of any material over secondmaterial B. Exemplary inert plasmas are derived from a gas selected fromthe group consisting of He, Ar, Ne, Xe, Kr and mixtures thereof. Aspecific exemplary preferred example for Ti, and by way of example only,includes a plasma generated by inductively coupled plasma, 2000 W forthe inductive source power, a substrate bias of 200 W, chamber pressureregulated to 10 mTorr, Ar flow at 100 sccm and a substrate temperatureof 500° C., preferably producing a plasma density of from 1×10¹¹ions/cm³ to 1×10¹³ ions/cm³.

In one implementation, the exposing to plasma might be void of ionimplantation, and in another might comprise ion implantation (by way ofexample only, plasma immersion ion implantation for example as describedin En et al., “Plasma Immersion Ion Implantation Reactor DesignConsiderations For Oxide Charging”, Surface and Coatings Technology 85(1996) 64–69). Further in one preferred embodiment, the method offorming the reaction product is entirely void of any ion implantation atthe interface.

In one embodiment, the plasma comprises some material which reacts withthe second material to form a reaction product fourth material over thereaction product third material. Such is diagrammatically depicted inFIG. 16. There shown is a plasma comprising a material C which reactswith second material B to form a reaction product fourth material BCover reaction product third material AB. Regardless, the stated first,second, third and fourth materials may be any one or combination ofinsulative, conductive and semiconductive materials. For example and byway of examples only, each of the first and second materials might beconductive, with the third material being insulative. Alternately, eachof the first and second materials could be conductive, with the thirdmaterial being conductive. Alternately, each of the first and secondmaterials could be insulative, with the third material being insulative.Alternately, each of the first and second materials could be insulative,with the third material being conductive. Alternately, one of the firstand second materials could be insulative and the other of the first andsecond materials being conductive, with the third material beinginsulative. Alternately, one of the first and second materials could beinsulative and the other of the first and second materials beingconductive, with the third material being conductive. Alternately, oneof the first and second materials could be conductive and the other ofthe first and second materials being semiconductive, with the thirdmaterial being conductive. Alternately, one of the first and secondmaterials could be conductive and the other of the first and secondmaterials being semiconductive, with the third material beinginsulative.

For example, FIG. 5 diagrammatically depicts a first material comprisingtitanium, a second material comprising aluminum, and a reaction productthird material comprising TiAl_(x). In this and all of the above andbelow examples, the stated first and second materials could of course bereversed, for example as depicted in FIG. 6 as compared to FIG. 5.

FIG. 7 depicts an example where the first and second materials are eachconductive, and the third material is insulative. Here, one of the firstand second materials comprises TiN and the other of the first and secondmaterials comprises B, with the third material comprising BN.

By way of example only, FIGS. 8 and 9 depict instances where the firstand second materials are each insulative, and the third material isinsulative. FIG. 8 depicts one of the first and second materials ascomprising boron carbide, and the other of the first and secondmaterials comprising SiO₂, with the third material comprising B₂O₃. FIG.9 depicts one of the first and second materials comprising boroncarbide, and the other of the first and second materials comprisingSi₃N₄, with the third material comprising BN.

FIG. 10 depicts an example where the first and second materials are eachinsulative, and the third material is conductive. In this example, oneof the first and second materials comprises carbon (i.e., diamond,graphite, etc.) and the other of the first and second materialscomprises SiO₂, with the third material comprising SiC.

FIG. 11 depicts an example where one of the first and second materialsis insulative and the other of the first and second materials isconductive, with the third material being conductive. Specifically, FIG.11 shows one of the first and second materials comprising titanium andthe other of the first and second materials comprising Si₃N₄, with thethird material comprising at least one of TiN or TiSi_(x).

FIG. 12 shows a similar example, but where the third material isinsulative. Specifically, one of the first and second materialscomprises SiO₂ and the other of the first and second material comprisesTi, with the third material comprising TiO₂.

FIGS. 13 and 14 depict examples wherein at least one of the first andsecond materials is semiconductive, and including wherein the other ofthe first and second materials is conductive. FIG. 13 depicts thesemiconductive materials comprising silicon, with the other of the firstand second materials comprising titanium, and with the third materialcomprising TiSi_(x). FIG. 14 depicts the semiconductive materialcomprising silicon, the other of the first and second materialscomprising titanium nitride, and with the third material comprisingTiSi_(x). Again with this and any of the examples stated herein, onlysome or all of the outermost layer might be consumed in the reaction.

FIG. 15 depicts an example where one of the first and second materialsis semiconductive, the other of the first and second materials isconductive, and the third material is insulative. Specifically, theredepicted is one of first and second materials comprising Si and theother of the first and second materials comprising RuO₂, with the thirdmaterial comprising SiO₂.

By way of example only, FIGS. 17 and 18 depict instances where theplasma comprises a material which reacts with the second material toform a reaction product fourth material over the reaction product thirdmaterial. The specific depicted examples are relative to plasma materialwhich comprises nitrogen, with such being depicted by N*, although otherreactive plasma materials are of course contemplated. FIG. 17 depictsthe second material as comprising elemental titanium, the first materialas comprising silicon, the third material as comprising titaniumsilicide, and the fourth material comprising titanium nitride. By way ofexample only, FIG. 18 depicts the first material comprising elementaltitanium, the second material comprising silicon, the third materialcomprising TiSi_(x), and the fourth material comprising silicon nitride.

In one exemplary preferred embodiment, the second material comprises atleast one of elemental metal or a metal compound rich in metal. In oneexemplary implementation, the second material consists essentially ofone of these materials. Exemplary preferred materials include Co, Ta,Ti, W, Pt, Rh, Ru, silicides thereof, including mixtures thereof andincluding mixtures of silicides. In this particular example as with theothers, the first and second materials as being proximate one another atan interface are capable of reacting with one another at some minimumreaction temperature when in an inert non-plasma atmosphere at apressure to form a metal silicide. As above, the interface is providedat a processing temperature which is at least 50° C. below the minimumreaction temperature and at the pressure. The substrate is exposed to aplasma effective to impart a reaction of the first material with thesecond material to form a metal silicide on the first material. Mostpreferably, the plasma is inert to reaction with both the silicon andthe at least one of the elemental metal and the metal compound, as wellas being inert to the deposition of any material over the secondmaterial. Other exemplary preferred attributes are as described above.

In this particular example, the preferred thickness range for the metalsilicide which is formed on the first material is from 5 Angstroms to100 Angstroms.

Processing as described in the above exemplary preferred embodiments canproduce certain unexpected advantages and results. However, suchadvantages or results do not constitute part of the invention unlessliterally appearing in a particular claim under analysis. For examplewith respect to any silicide formation, the exposing and reaction canresult in better control (less variation) in the thickness of the metalsilicide formed by the reaction. Accordingly in one implementation, theexposing and reaction are effective to form all conductive metalsilicide formed over the substrate by the reaction to have no more than10% thickness variation as determined as the percentage of the thicknessportion of the conductive metal silicide formed by the reaction. Inanother preferred implementation, such thickness variation is from 1% to3%, and in another preferred embodiment to have no more than 1% of suchthickness variation.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

1. A method of forming a reaction product, comprising: providing asemiconductor substrate comprising a first material; forming a secondmaterial over the first material, the first and second materials beingof different compositions and being proximate one another at aninterface, the first and second materials as being proximate one anotherat the interface being capable of reacting with one another at someminimum reaction temperature when in an inert non-plasma atmosphere at apressure; providing the interface at a processing temperature which isat least 50° C. below the minimum reaction temperature and at thepressure; and with the interface at the processing temperature and atthe pressure, exposing the substrate to a plasma effective to impart areaction of the first material with the second material to form areaction product third material of the first and second materials overthe first material.
 2. The method of claim 1 wherein the first andsecond materials contact one another at the interface prior to theexposing.
 3. The method of claim 1 wherein the first and secondmaterials do not contact one another at the interface prior to theexposing.
 4. The method of claim 1 wherein the exposing starts prior toproviding the interface at the processing temperature at the pressure.5. The method of claim 1 wherein the exposing starts after providing theinterface at the processing temperature at the pressure.
 6. The methodof claim 1 wherein the second material is formed to a thickness nogreater than 75 Angstroms.
 7. The method of claim 6 wherein the secondmaterial is formed to a thickness no greater than 25 Angstroms.
 8. Themethod of claim 1 wherein the plasma is inert to reaction with both thefirst and second materials and inert to deposition of material over thesecond material.
 9. The method of claim 8 wherein the plasma is derivedfrom a gas selected from the group consisting of He, Ar, Ne, Xe, Kr andmixtures thereof.
 10. The method of claim 1 wherein the plasma comprisesa material which reacts with the second material to form a reactionproduct fourth material over the reaction product third material. 11.The method of claim 10 wherein the plasma material comprises nitrogen,the first material comprises silicon, the second material compriseselemental titanium, the third material comprises titanium silicide, andthe fourth material comprises titanium nitride.
 12. The method of claim10 wherein the plasma material comprises nitrogen, the first materialcomprises elemental titanium, the second material comprises silicon, thethird material comprises titanium silicide, and the fourth materialcomprises silicon nitride.
 13. The method of claim 1 wherein the firstand second materials are each conductive.
 14. The method of claim 13wherein the third material is conductive.
 15. The method of claim 14wherein one of the first and second materials comprises titanium and theother of the first and second materials comprises aluminum, the thirdmaterial comprising TiAl_(x).
 16. The method of claim 13 wherein thethird material is insulative.
 17. The method of claim 16 wherein one ofthe first and second materials comprises TiN and the other of the firstand second materials comprises B, the third material comprising BN. 18.The method of claim 1 wherein the first and second materials are eachinsulative.
 19. The method of claim 18 wherein the third material isconductive.
 20. The method of claim 19 wherein one of the first andsecond materials comprises carbon and the other of the first and secondmaterials comprises SiO₂, the third material comprising SiC.
 21. Themethod of claim 18 wherein the third material is insulative.
 22. Themethod of claim 21 wherein one of the first and second materialscomprises boron carbide and the other of the first and second materialscomprises SiO₂, the third material comprising B₂O₃.
 23. The method ofclaim 21 wherein one of the first and second materials comprises boroncarbide and the other of the first and second materials comprises Si₃N₄,the third material comprising BN.
 24. The method of claim 1 wherein oneof the first and second materials is insulative and the other of thefirst and second materials is conductive.
 25. The method of claim 24wherein the third material is conductive.
 26. The method of claim 25wherein one of the first and second materials comprises titanium and theother of the first and second materials comprises Si₃N₄, the thirdmaterial comprising at least one of TiN or TiSi_(x).
 27. The method ofclaim 24 wherein the third material is insulative.
 28. The method ofclaim 27 wherein one of the first and second materials comprises SiO₂and the other of the first and second materials comprises Ti, the thirdmaterial comprising TiO₂.
 29. The method of claim 1 wherein at least oneof the first and second materials is semiconductive.
 30. The method ofclaim 29 wherein the third material is conductive.
 31. The method ofclaim 30 wherein the semiconductive material comprises silicon, theother of the first and second materials comprises elemental titanium,and the third material comprising TiSi_(x).
 32. The method of claim 30wherein the semiconductive material comprises silicon, the other of thefirst and second materials comprises titanium nitride, and the thirdmaterial comprising TiSi_(x).
 33. The method of claim 29 wherein thethird material is insulative.
 34. The method of claim 33 wherein one ofthe first and second materials comprises Si and the other of the firstand second materials comprises RuO₂, the third material comprising SiO₂.35. The method of claim 1 wherein the processing temperature is nogreater than 300° C. below the minimum reaction temperature.
 36. Themethod of claim 1 wherein the processing temperature is no greater than100° C. below the minimum reaction temperature.
 37. The method of claim1 wherein the processing temperature is no greater than 75° C. below theminimum reaction temperature.
 38. The method of claim 1 wherein theprocessing temperature is no greater than 60° C. below the minimumreaction temperature.
 39. The method of claim 1 wherein the thirdmaterial is conductive.
 40. The method of claim 39 wherein the thirdmaterial comprises a silicide.
 41. The method of claim 40 wherein theexposing is effective to form all conductive metal silicide on the firstmaterial to have no more than 10% thickness variation as determined of athickest portion of said conductive metal silicide formed by thereaction.
 42. The method of claim 40 wherein the exposing is effectiveto form all conductive metal silicide on the first material to have nomore than 1% thickness variation as determined of a thickest portion ofsaid conductive metal silicide formed by the reaction.
 43. The method ofclaim 40 wherein the exposing is effective to form all conductive metalsilicide on the first material to have from 1% to 3% thickness variationas determined of a thickest portion-of said conductive metal silicideformed by the reaction.
 44. The method of claim 39 wherein the thirdmaterial comprises TiAl_(x).
 45. The method of claim 1 wherein the thirdmaterial is insulative.
 46. The method of claim 1 wherein the plasmaduring the exposing has a plasma density from 1×10¹¹ ions/cm³ to 1×10¹³ions/cm³.
 47. The method of claim 1 wherein the exposing comprises asubstrate bias.
 48. The method of claim 1 wherein the plasma comprisesplasma immersion ion implantation.
 49. The method of claim 1 wherein theexposing is void of ion implantation.
 50. The method of claim 1 beingvoid of ion implantation at the interface.
 51. A method of forming areaction product, comprising: providing a semiconductor substratecomprising a first material; forming a second material on the firstmaterial, the first and second materials being of different compositionsand contacting against one another at an interface, the first and secondmaterials as contacting against one another at the interface beingcapable of reacting with one another at some minimum reactiontemperature when in an inert non-plasma atmosphere at a pressure;providing the interface at a processing temperature which is at least50° C. below the minimum reaction temperature and at the pressure; andwith the interface at the processing temperature and at the pressure,exposing the substrate to a plasma effective to impart a reaction of thefirst material with the second material to form a reaction product thirdmaterial of the first and second materials over the first material, theplasma being inert to reaction with both the first and second materialsand inert to deposition of material over the second material.
 52. Themethod of claim 51 wherein the second material is formed to a thicknessno greater than 75 Angstroms.
 53. The method of claim 52 wherein thesecond material is formed to a thickness no greater than 25 Angstroms.54. The method of claim 51 wherein the exposing starts prior toproviding the interface at the processing temperature at the pressure.55. The method of claim 51 wherein the exposing starts after providingthe interface at the processing temperature at the pressure.
 56. Themethod of claim 51 wherein the first and second materials are eachconductive.
 57. The method of claim 56 wherein the third material isconductive.
 58. The method of claim 57 wherein one of the first andsecond materials comprises titanium and the other of the first andsecond materials comprises aluminum, the third material comprisingTiAl_(x).
 59. The method of claim 56 wherein the third material isinsulative.
 60. The method of claim 59 wherein one of the first andsecond materials comprises TiN and the other of the first and secondmaterials comprises B, the third material comprising BN.
 61. The methodof claim 51 wherein the first and second materials are each insulative.62. The method of claim 61 wherein the third material is conductive. 63.The method of claim 62 wherein one of the first and second materialscomprises carbon and the other of the first and second materialscomprises SiO₂, the third material comprising SiC.
 64. The method ofclaim 61 wherein the third material is insulative.
 65. The method ofclaim 64 wherein one of the first and second materials comprises boroncarbide and the other of the first and second materials comprises SiO₂,the third material comprising B₂O₃.
 66. The method of claim 64 whereinone of the first and second materials comprises boron carbide and theother of the first and second materials comprises Si₃N₄, the thirdmaterial comprising BN.
 67. The method of claim 51 wherein one of thefirst and second materials is insulative and the other of the first andsecond materials is conductive.
 68. The method of claim 67 wherein thethird material is conductive.
 69. The method of claim 68 wherein one ofthe first and second materials comprises titanium and the other of thefirst and second materials comprises Si₃N₄, the third materialcomprising at least one of TiN or TiSi_(x).
 70. The method of claim 67wherein the third material is insulative.
 71. The method of claim 70wherein one of the first and second materials comprises SiO₂ and theother of the first and second materials comprises Ti, the third materialcomprising TiO₂.
 72. The method of claim 51 wherein at least one of thefirst and second materials is semiconductive.
 73. The method of claim 72wherein the third material is conductive.
 74. The method of claim 73wherein the semiconductive material comprises silicon, the other of thefirst and second materials comprises titanium, the third materialcomprising TiSi_(x).
 75. The method of claim 72 wherein the thirdmaterial is insulative.
 76. The method of claim 75 wherein one of thefirst and second materials comprises Si and the other of the first andsecond materials comprises RuO₂, the third material comprising SiO₂. 77.The method of claim 51 wherein the processing temperature is no greaterthan 300° C. below the minimum reaction temperature.
 78. The method ofclaim 51 wherein the processing temperature is no greater than 100° C.below the minimum reaction temperature.
 79. The method of claim 51wherein the processing temperature is no greater than 75° C. below theminimum reaction temperature.
 80. The method of claim 51 wherein theprocessing temperature is no greater than 60° C. below the minimumreaction temperature.
 81. The method of claim 51 wherein the thirdmaterial is conductive.
 82. The method of claim 81 wherein the thirdmaterial comprises a silicide.
 83. The method of claim 81 wherein thethird material comprises TiAl_(x).
 84. The method of claim 51 whereinthe third material is insulative.
 85. The method of claim 51 wherein theplasma during the exposing has a plasma density from 1×10¹¹ ions/cm³ to1×10¹³ ions/cm³.
 86. The method of claim 51 wherein the exposingcomprises a substrate bias.
 87. The method of claim 51 wherein theplasma comprises plasma immersion ion implantation.
 88. The method ofclaim 51 wherein the exposing is void of ion implantation.
 89. Themethod of claim 51 being void of ion implantation at the interface. 90.A method of forming a conductive metal silicide by reaction of metalwith silicon, comprising: providing a semiconductor substrate comprisinga first material, the first material comprising silicon in elementalform; forming a second material over the first material, the secondmaterial comprising at least one of an elemental metal or a metalcompound rich in metal, the first and second materials being proximateone another at an interface, the first and second materials as beingproximate one another at the interface being capable of reacting withone another at some minimum reaction temperature when in an inertnon-plasma atmosphere at a pressure to form a metal silicide; providingthe interface at a processing temperature which is at least 50° C. belowthe minimum reaction temperature and at the pressure; and with theinterface at the processing temperature and at the pressure, exposingthe substrate to a plasma effective to impart a reaction of the firstmaterial with the second material to form a metal silicide on the firstmaterial, the plasma being inert to reaction with both the silicon andthe at least one of the elemental metal and the metal compound and inertto deposition of material over the second material.
 91. The method ofclaim 90 wherein the second material is formed to a thickness no greaterthan 75 Angstroms.
 92. The method of claim 91 wherein the secondmaterial is formed to a thickness no greater than 25 Angstroms.
 93. Themethod of claim 90 wherein the exposing starts prior to providing theinterface at the processing temperature at the pressure.
 94. The methodof claim 90 wherein the exposing starts after providing the interface atthe processing temperature at the pressure.
 95. The method of claim 90wherein the second material comprises elemental metal.
 96. The method ofclaim 95 wherein the second material consists essentially of elementalmetal.
 97. The method of claim 90 wherein the second material comprisesa metal compound rich in metal.
 98. The method of claim 97 wherein thesecond material consists essentially of one or more metal compounds richin metal.
 99. The method of claim 90 wherein the silicon and the atleast one of a metal and metal compound contact one another at theinterface prior to the exposing.
 100. The method of claim 90 wherein thesilicon and the at least one of a metal and metal compound do notcontact one another at the interface prior to the exposing.
 101. Themethod of claim 90 wherein the plasma is derived from a gas selectedfrom the group consisting of He, Ar, Ne, Xe, Kr and mixtures thereof.102. The method of claim 90 wherein the processing temperature is nogreater than 300° C. below the minimum reaction temperature.
 103. Themethod of claim 90 wherein the processing temperature is no greater than10° C. below the minimum reaction temperature.
 104. The method of claim90 wherein the processing temperature is no greater than 75° C. belowthe minimum reaction temperature.
 105. The method of claim 90 whereinthe processing temperature is no greater than 60° C. below the minimumreaction temperature.
 106. The method of claim 90 wherein the plasmaduring the exposing has a plasma density from 1×10¹¹ ions/cm³ to 1×10¹³ions/cm³.
 107. The method of claim 90 wherein the exposing comprises asubstrate bias.
 108. The method of claim 90 wherein the metal silicideformed on the first material has a thickness of from 5 Angstroms to 100Angstroms.
 109. The method of claim 90 wherein the exposing is effectiveto form all conductive metal silicide on the first material to have nomore than 10% thickness variation as determined of a thickest portion ofsaid conductive metal suicide formed by the reaction.
 110. The method ofclaim 90 wherein the exposing is effective to form all conductive metalsilicide on the first material to have no more than 1% thicknessvariation as determined of a thickest portion of said conductive metalsilicide formed by the reaction.
 111. The method of claim 90 wherein theexposing is effective to form all conductive metal silicide on the firstmaterial to have from 1% to 3% thickness variation as determined of athickest portion of said conductive metal silicide formed by thereaction.
 112. The method of claim 90 wherein the plasma comprisesplasma immersion ion implantation.
 113. The method of claim 90 whereinthe exposing is void of ion implantation.
 114. The method of claim 90being void of ion implantation at the interface.